An invertigation of mechanisms of self-pumped phase conjugation (SPPC) in BaTio3: Ce crystal in the green, λ = 514. 5 nm on pump beam parameters, such as the beam diameter, the incidence angle and the position was reported. It was found that the SPPC mechanism changed from a "cat" (FWM-TIM) mechanism to a stimulated photorefractive backscattering and four- wave-mixing (FWM- SPB) when the pump beam diameter, the incidence angle and position were varied, with a transition of FWM-TIR + FWM-SPB mechanism coexisted.